BEIRUT (AP) — Activists say Syrian rebels have taken control of an airport in the country’s east along the border with Iraq after days of heavy fighting with the forces of President Bashar Assad.

Rami Abdul-Rahman, the chief of the Britain-based Syrian Observatory for Human Rights says opposition fighters overran the Hamdan airport in the oil-rich province of Deir el-Zour on Saturday. The airport, near the border town of al-Boukamal, has been turned into a military base during Syria’s 20 months of conflict that has left over 36,000 people dead.

Rebels had been making advances in al-Boukamal town for weeks. On Thursday, they seized control of the military security building and a military checkpoint at the edge of the border town.

At least four rebels were killed in the ongoing battle, Abdul-Rahman said.